D. S. Ahearn*(1), R. A. Dahlgren(1) (1) Dept. of Land, Air and Water Resources, University

D. S. Ahearn*(1), R. A. Dahlgren(1) (1) Dept. of Land, Air and Water Resources, University of California, Davis, CA 95616

NUTRIENT EXPORT FOLLOWING REMOVAL OF A LOW-HEAD DAM, MURPHY CREEK, CA.

A 2.5 meter dam in the Murphy Creek catchment (1,338 hectares) located in the lower Mokelumne River watershed was removed in August 2003 in an effort to restore fluvial habitat for anadromous fishes. The goal of this study was to quantify the impacts of this dam removal on water quality and to characterize the processes driving the hydrobiogeochemistry of the restored reach. During the restoration process organic-rich sediment behind the dam was left undisturbed. Prior to removal N mineralization from this organic-rich sediment created high ammonium concentrations that were largely retained by the benthic deposits. After the pond was drained this pool of ammonium was exposed to oxic conditions and nitrification created high nitrate export from the restored reservoir reach. Longitudinal transect data of sediments and overlying channel water reveal a seasonal pattern where high sediment ammonium (max = 58.9 mg/kg) is correlated with elevated nitrate (max = 0.7 mg/l) and ammonium (max = 1.1 mg/l) in overlying waters during the fall and early winter. Later in the winter microbial activity slows and so does the nitrification process; transects reveal minimal nitrate production through the restored reach during this period. In the spring and summer aquatic plant communities take up N masking any N production from sediments. Input and output flux analysis indicates that the restored reach yields substantial amounts of N. Our analyses suggest that nitrogen mineralization in the sediments is the source of this N and that future restoration projects should be aware of the possibility of nitrogen leaching from reservoir sediments following dam removal.
Allen*, P., B. Hodge, J.J. Cech, Jr.Department of Wildlife, Fish, and Conservation Biology, and the Center for Aquatic Biology and Aquaculture, University of California, Davis, CA 95616

TOWARDS PROTECTING SACRAMENTO-SAN JOAQUIN WATERSHED GREEN STURGEON: SWIMMING PERFORMANCE RELATIONSHIPS WITH SEAWATER TOLERANCE AND TEMPERATURE

Juvenile, anadromous green sturgeon (Acipenser medirostris) move from riverine freshwater habitats downstream into the ocean. This transition is very similar to those of many juvenile salmonid species during their parr-smolt transformation, when they achieve seawater tolerance. Smolting salmonids generally show a marked decrease in maximum aerobic swimming performance (Ucrit) compared to freshwater parr. We tested the hypothesis that juvenile green sturgeon decrease Ucrit during a corresponding developmental period. Swimming experiments were run concurrently with salinity tolerance studies (both at 19ºC), which showed increasing tolerance to full-strength sea water (33 ppt) during the ages (73-177 days post hatch) and sizes (15-45 cm total length [TL]) studied. Younger and smaller juvenile green sturgeon, which had not reached seawater tolerance, had a positive relationship (p<0.0007, n= 59) of Ucrit (cm/s) with TL. However, the older and larger sturgeon, which had reached seawater tolerance (>30.9 cm TL), had a negative relationship of Ucrit with TL (p<0.029, n=19). Presumably this decreased aerobic swimming performance facilitates their downstream migration to the ocean, via a decreased ability to resist strong river currents. The similarity of this Ucrit –seawater tolerance relationship to that seen in many smolting salmonids indicates either the repeated evolutionary emergence or a long-term (>200 million years) conservation of this pattern in present-day anadromous fishes. In a second experiment, seawater-tolerant juveniles tested at elevated (24ºC) temperatures showed significantly increased Ucrit, compared with those tested at 19ºC. These results could indicate either overall, enhanced aerobic swimming or potentially reduced downstream migration in strong currents, at the warmer temperature. In conclusion, environmental variables such as water velocity and water temperature should be considered in efforts to protect Sacramento-San Joaquin Watershed green sturgeon. We thank the Anadromous Fish Restoration Program (USFWS & USBR) and CALFED for funding, and the Yurok Tribe for brood fish.
Alpers, C. N.* (1), M. P. Hunerlach (1), M. Marvin-DiPasquale (2), N. P. Snyder (3, 4), D. P. Krabbenhoft (5). (1) U.S. Geological Survey (USGS), Placer Hall, 6000 J Street, Sacramento, CA 95819. (2) USGS, MS 480, 345 Middlefield Road, Menlo Park, CA 94025. (3) Department of Geology and Geophysics, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467. (4) USGS, 400 Natural Bridges Drive, Santa Cruz, CA 95060. (6) USGS, 8505 Research Way, Middleton, WI 53562.

MERCURY AND METHYLMERCURY IN THE UPPER YUBA RIVER WATERSHED: FLUVIAL TRANSPORT AND RESERVOIR SEDIMENTATION

The potential introduction of anadromous fish to the upper Yuba River watershed (upstream of Englebright Dam) has raised questions concerning possible risks associated with exposure to mercury contamination from historical gold mining. These concerns were investigated by monitoring mercury (Hg) and methylmercury (MeHg) concentrations in water, suspended sediment, and reservoir-bed sediment during 2001–2003.

Concentrations of Hg and MeHg were determined in both unfiltered and 0.45-micrometer-filtered water, along with suspended-sediment concentration (SSC) at gaging stations on the South Yuba River (SY), the Middle Yuba River (MY), and the Yuba River below Englebright Dam. At SY and MY, there were positive correlations between discharge, SSC, and Hg in unfiltered water. Average Hg in suspended silt and clay at SY was about 350 nanograms per gram (ng/g) dry sediment. The highest concentrations of Hg and SSC relative to discharge at SY and MY occurred during rising limbs of early-wet-season storms. About 25% of unfiltered MeHg analyses were > 0.10 nanograms per liter, mostly during storms.

Deep sediment coring during 2002 penetrated the entire post-dam sediment pile at six locations in Englebright Lake. Sediment thickness ranged from 6 m near Englebright Dam to 33 m in the mid-reservoir area. Sediment Hg concentrations ranged from 2 to 1,150 ng/g (median 139 ng/g, n=166); MeHg concentrations ranged from 0.007 to 6.8 ng/g (median 0.36 ng/g; n=166). The persistence of moderately elevated MeHg concentrations throughout the sediment pile suggests several causative factors, including rapid burial and preservation of the deposited MeHg, moderately low rates of MeHg demethylation, and (or) persistent Hg methylation in relatively organic-rich sediments.

Exposure levels of MeHg in water and sediment in upper Yuba River watershed may represent significant ecological risk to aquatic species. Potential MeHg exposure and associated risk should be considered in the development of anadromous-fish-introduction scenarios above Englebright Dam.
Anderson*, J. CA Dept. of Water Resources, 1416 Ninth Street, Room 215-17, Sacramento, CA 95814.

IMPACTS OF CLIMATE CHANGE ON MANAGEMENT OF CALIFORNIA’S WATER RESOURCES: PART III-DELTA WATER QUALITY

Problem Statement: A joint California Department of Water Resources (DWR) and U. S. Bureau of Reclamation (USBR) Climate Change Work Team is investigating methods for assessing potential impacts of climate change on California’s water resources using a framework that provides results that are relevant to water resources planners (see Part I). One component of those investigations focuses on evaluating potential impacts of climate change on water quality in the Sacramento-San Joaquin Delta.

Approach: Impacts of climate change on Delta water quality are being investigated using a multi-step modeling approach: 1) identify climate change scenarios, 2) determine changes in natural runoff for each scenario, 3) assess changes in CVP and SWP operations using CALSIM II, and 4) evaluate impacts on Delta water quality using the Delta Simulation Model 2 (DSM2). This study examines climate predictions from two General Circulation Models (GCMs) and three scenarios that represent incremental changes in air temperature of 1.5°C, 3.0°C, and 5.0°C, representative of short, mid, and long term climate change, respectively. Delta inflows for each scenario are provided by simulation results from the operations model CALSIM II which was run for the D1641 regulatory environment for each of the selected scenarios at a future level of land use development (see Part II). DSM2 utilizes those Delta inflows to simulate water quality for each scenario.

Results: Assessment of water quality impacts of climate change focuses on municipal and agricultural standards for chlorides and electro conductivity (EC). Results are presented for the four urban intakes and for four D1641 agricultural standard sites. Effects of projected land use changes on water quality are compared to the potential climate change impacts to determine their relative impacts on Delta water quality.

Relevance: These results are relevant to the CALFED objectives of water quality and water supply reliability.
Anderson*, S.L. (1), A.J. Brooks (3), G.N. Cherr (1), R.M. Higashi (2), S.G. Morgan (1), R.M. Nisbet (3), and R. S. Carr (4). (1) Bodega Marine Laboratory (BML), PO Box 247, Bodega Bay, CA 94923. (2) Center for Health & Environment, University of California, Davis (UCD), One Shields Avenue, Davis, CA 95616. (3) Marine Science Institute, University of California, Santa Barbara (UCSB), Santa Barbara, CA 93106. (4) US Geological Survey (USGS), Columbia Environmental Research Center, Marine Ecotoxicology Research Station, Texas A&M University-Corpus Christi, NRC Suite 3200, 6300 Ocean Drive, Corpus Christi, TX 78412.

INTEGRATING INDICATORS OF TOXICANT EXPOSURE AND EFFECT IN SALT MARSH SPECIES: COMPLEMENTING THE ECO-RISK PARADIGM.

Ecological risk assessment in estuarine systems relies heavily on use of toxicity tests, analytical chemistry, and ecosystem census to estimate risk to aquatic life. While this approach has been valuable for many management goals over at least two decades, complementary approaches are needed. These should provide improved: linkage to the ecological system under investigation, assessment of multiple stressors, procedures for spatial, temporal, or biological scaling. We propose a complementary framework in which chemical exposures and effects are characterized in strategically-selected salt marsh species at multiple scales. This makes possible: 1) direct evaluation of ecologically-relevant responses and 2) analysis and diagnosis of multiple stressors. We sampled several marsh sites in Northern and Southern California for population-level, and biomarker responses in wetland plants, shore crabs (Pachygrapsus crassipes), and mudsucker fish (Gillichthys mirabilis). We also conducted analytical chemistry and ecosystem censuses at each site. A comparison to toxicity test responses has been performed at a more limited number of stations. Data for a key marsh restoration site indicate that the application of toxicity tests to the salt marsh environment is limited by ammonia interferences; however, toxicity attributable to organic compounds is implicated. Data on resident species includes: decreased biomass (by remote sensing and field measurement) of wetland plants as well as endocrine disruption and apoptosis in mudsuckers. More preliminary findings also point to decreased reproductive success in shore crabs and depressed growth rates of fish relative to reference sites. These data indicate that an integrated suite of techniques linking sublethal effects to ecologically relevant endpoints in resident organisms may provide practical information that can be used to inform decisions within CALFED about marsh restoration and monitoring. This research has been supported by a grant from the CALFED Bay-Delta Program to the Pacific Estuarine Ecosystem Indicator Research (PEEIR) Consortium under State Resources Agency Agreement #4600002051.
Andrews*, E.S., P.B. Williams. Philip Williams & Associates, Ltd. (PWA), 720 California St., Suite 600, San Francisco, CA 94108.

FUNCTIONAL FLOODPLAINS: HOW MUCH DO WE HAVE NOW, HOW MUCH CAN WE RESTORE?

The Ecosystem Restoration Program Plan (CALFED 2000) identifies re-establishment of significant areas of active, ecologically-significant, floodplain inundation. Such floodplains must be recognizable in terms of both landscape and process to be “functional” for ecological purposes. Yet a scientifically-defensible definition of functional floodplain has not been proposed or adopted for the purpose of evaluating this goal. In addition, no data exists that quantifies the amount of physically-available floodplain that might be available if reconnected, or even the amount of functional floodplain presently remaining in the Central Valley.

Using current estimates of riparian and riparian wetland areas as proxies for floodplain area (an imprecise approach, as there is not an exact correspondence), there may be as little as 3% of the Central Valley’s historic floodplains still in existence and active at the present time. There are significant constraints to restoring floodplain areas, including urbanization, the development of infrastructure, and the widespread loss of physical accessibility to floodplains as a result of both hydrologic modification (reduced floods) and morphologic change (incised channels). This presentation will propose an approach to defining a functional floodplain and explore potential methods to identify and quantify both existing and potential areas of functional floodplain in the Central Valley. The critical value of this information will be to not only highlight the best areas for potential restoration activities, but also the methods and scale at which such activities must be undertaken to achieve the Ecosystem Restoration Program’s floodplain connectivity and ecosystem enhancement goals in the Central Valley. This information is necessary to effectively target program dollars and act on floodplain restoration opportunities before they are lost.
Ashley*, R.P.(1), J.J. Rytuba (1). (1)U.S. Geological Survey (USGS), Menlo Park, 345 Middlefield Rd. Mail Stop 901, Menlo Park, CA 94025

MERCURY ASSOCIATED WITH GOLD DREDGE TAILINGS IN THE CLEAR CREEK AND TRINITY RIVER WATERSHEDS, CALIFORNIA

From 1900 until the 1960s placer gold deposits in northern California were mined mainly by dredging. The alluvial material processed was screened and coarse clasts (usually >1 cm) were discharged using a stacker. The finer material was washed through sluice boxes charged with mercury to capture fine gold by amalgamation. Thus release of mercury and subsequent uptake by biota is of concern in restoration projects that involve moving or using mercury-contaminated dredge tailings. The purpose of this study is to determine distribution, speciation, and mobility of mercury in tailings from floating dredges operated on lower Clear Creek and the middle Trinity River, in the eastern Klamath Mountains. Stacker tailings deposited above water level have relatively low mercury concentrations, no more than about twice background values (10-60 ng/g). Stacker tailings deposited below water level contain fine interstitial material (silt-clay), which was released into the dredge pond during digging or cycled through the sluices, and dispersed into the coarser tailings by infiltration. These fines, which also settled to form lenses in the coarser tailings, have as much as 150 ng/g mercury. Pebbly sand lenses in the tailings, which represent discharge from the dredge sluices, contain as much as 4000 ng/g mercury. Thus mercury concentrations vary widely in dredge tailings, but materials that may be of concern such as sluice sands can be recognized in the field, using knowledge of tailings stratigraphy and history of dredging operations. Sequential extraction studies reveal that 40-60% of the elemental mercury introduced to the tailings has been converted to soluble and base-leachable organically bound forms; 5-20% has been converted to mercury sulfide (HgS). Although methylmercury concentrations in undisturbed dry tailings are generally very low, fines released from tailings and introduced to methylating environments result in high methylmercury levels in water, sediments, and biota.
Athearn*, N. D. (1), J. Y. Takekawa (1), A. K. Miles (2), D. H. Schoellhamer (3), and G. G. Shellenbarger (3). (1) U.S. Geological Survey (USGS) Western Ecological Research Center (WERC) 505 Azuar Dr., Vallejo, CA 94592. (2) USGS WERC 1 Shields Ave., Univ. of Calif., Davis, CA 95616. (3) USGS Sacramento State Univ., Placer Hall, Sacramento, CA 95819.